The present invention relates to mechanisms for securing doors from being opened by small children, and in particular, to a device suitable for doors with lever-type door handles.
Architectural doors may have a latch mechanism holding the door closed and operated by means of a doorknob. Particularly for interior doors, the latch mechanism may be without a lock, and therefore readily opened by anyone turning the doorknob.
Parents with small children who wish to secure a door, for example, a door leading to stairs or other hazards, may make use of an add-on “safety lock” that prevents the child from opening the door. A commonly available safety lock for standard doorknobs covers the doorknob with a loosely fitting shell which rotates freely around the doorknob. A child grasping the shell can turn only the shell and not the contained knob. An adult with greater hand strength may compress the shell against the doorknob so as to enable rotation of the doorknob through the shell. This type of safety lock differentiates between adults and children in part by hand strength and requires that the doorknob be rotationally symmetric.
In recent years, such symmetric doorknobs have given way to lever handles which can be easier for the infirm and handicapped to actuate. A safety lock using a rotating shell design does not work with such lever handle systems, which are not rotationally symmetric, and have a wide variety of lever sizes.
Nevertheless, it is often desired to secure doors having such lever handles from opening by small children, and in fact, lever handles may in some cases be easier for small children to open, to the extent that the child may be drawn to reach up and hang upon the lever.